A. DEFINITION The Protein Identification and Localization (PIL) Core is a restructured core that has evolved from aspects of two previous cores, the Cell Biology and Cell Imaging Core which focused on cellular imaging and the Peptides and Proteomics Core which had a dual service of providing synthetic peptides and identifying proteins by mass spectrometry. While cell biological methods are now standard in most laboratories and peptide synthesis can be obtained both from University and commercial sources, what was unique about the two previous cores was their synergy in identifying and localizing proteins. These aspects are preserved and enhanced by the structure of the new PIL Core and build on the longstanding collaborative interactions between Drs. Williams, Andrews and Ernst. They also build on the fact that this type of research requires complex and expensive equipment not available in individual laboratories. The PIL Core is designed to provide information on the identity of proteins by mass spectrometry, either as individual proteins purified in an investigator's laboratory and usually separated as a band or spot by gel electrophoresis or globally as a mixture of proteins in a protein complex or organelle. Information is also be provided on post-translational modifications of proteins and on quantitative changes in protein content. Once a protein is identified, the Core can provide information on the localization of the protein in live and fixed cells and their changes over time and in response to physiological and pathophysiological perturbation. It is centered around microscopic imaging and quantitative analysis of digital information obtained primarily by laser scanning confocal microscopy (LSCM) and multiwavelength fluorescence imaging, although traditional electron microscopy of fixed and embedded specimens is also available for fine structure analysis. Modern biomedical research is characterized both by its interdisciplinary nature and by its dependence on increasingly sophisticated instrumentation and informatics. Although the goal is to look at a tissue, disease, or organism as a complex integrated system, we are still developing an understanding of the structure and function of the components which are often cell type dependent. With the mapping of the genome, attention has shifted to the more complex world of the proteome. Complete inventories of most mammalian protein complexes or organelles are yet to be completed and they often vary between cell types, during the cell cycle, and during various stages of development. Thus identification of proteins, their post-translational modifications, dynamic interactions and cellular localization, all in time and space and in a quantitative manner, is a daunting task that almost all laboratory scientists in the GI Peptide Center encounter in their research. These questions can be approached through the tools of the PIL Core, very often in concert with the Molecular Biology Core and national genomic resources such as the NCBI. The new PIL Core is built around expertise in the director's laboratories, and the availability of sophisticated instrumentation in three existing facilities, the Michigan Proteome Core, the Morphology and Imaging Laboratory (MIL) of the Department of Cell and Developmental Biology and the Michigan Diabetes Research and Training Center (MDRTC) which maintain facilities discussed in detail below for sophisticated mass spectrometry and high resolution microscopy. This arrangement is facilitated by the fact that Dr Andrews directs the Michigan Proteome Core, Dr Williams directs the Microscopy and Image Analysis Laboratory of the MDRTC and Dr Ernst has a long standing affiliation with the MIL. All three entities have established personnel and a recharge structure and are currently being use by GI Center members. While the Protein Identification and Localization Core will make use of the available highly sophisticated instrumentation, it also is built around the over 90 years of proteomic, cell biology and imaging expertise of Drs. Williams, Andrews and Ernst which has been primarily devoted to GI Tissues. Experienced Core staff, including Drs. Walker, Strahler and Mr. Nelson, will directly assist Center Investigators and carry out the procedures of the Core. All Core personnel will demonstrate and teach techniques to GI Center investigators, trainees and technicians. Finally another mission of the Core is to initiate, implement and disseminate new and innovative techniques in proteomics and cell imaging.